1. Field of the Invention
This invention relates to a wireless transmission system or apparatus and a wireless transmission method.
2. Description of the Related Art
For example, LVDS (Low Voltage Differential Signaling) is known as a method of implementing high-speed signal transmission between electronic apparatus disposed in a spaced relationship by a comparatively short distance from each other (for example, in a few centimeters to ten and several centimeters) or within an electronic apparatus. However, together with further increase in quantity of transmission data and speed of transmission in recent years, increase of the power consumption, increase of the influence of signal distortion by reflection and so forth, increase of unnecessary radiation and so forth have become subjects. For example, the LVDS exhibits its limit to a case wherein an image signal (including a picked up image signal), a signal of a computer image or a like signal is transmitted at a high speed (on the real time basis) within an apparatus.
In order to cope with the problems by increase of the transmission speed of transmission data, it seems a promising idea to increase the number of wires to transmit signals in parallel while the transmission speed is dropped per one signal line. However, this countermeasure gives rise to increase of input and output terminals. This may require complication of a printed board and cable wires and increase of the semiconductor chip size. Further, since a large amount of high-speed data is transmitted by wires, electromagnetic field interference becomes a problem.
Problems in the LVDS or a technique of increasing the number of wires all arise from transmission of a signal by means of electric wires. Therefore, as a technique for solving problems arising from transmission of a signal by means of electric wires, a technique has been proposed wherein a signal is transmitted eliminating electric wires as disclosed, for example, in Japanese Patent Laid-Open No. 2005-204221 (hereinafter referred to as Patent Document 1) and Japanese Patent Laid-Open No. 2005-223411 (hereinafter referred to as Patent Document 2).
Patent Documents 1 and 2 describe utilization of such standards as IEEE 802.11a/b/g wherein the 2.4 GHz band or the 5 GHz band is used.
Here, since the number of signals connected by electric wires is not limited to one, if it is tried to modify the electric wires so that all signals are transmitted wirelessly using the same frequency, then a problem of interference occurs. In order to eliminate the problem of interference, it seems a promising idea to apply, for example, time division multiplexing or frequency division multiplexing.
However, the time division multiplexing provides a problem that transmission and reception of signals cannot be carried out in parallel while the frequency division multiplexing provides another problem that the bandwidth has to be increased.
In this manner, where it is intended to transmit signals wirelessly in signal transmission between apparatus spaced by a comparatively short distance from each other or within an apparatus, there still remain faults.